Enzymatic depolymerization of polysaccharides is a key step in the production of fuels and chemicals from lignocellulosic biomass, and discovery of synergistic biomass-degrading enzyme paradigms will enable improved conversion processes. Historically, understanding the enzymatic saccharification mechanisms of plant cell walls has been hindered by poorly characterized substrates, limited enzyme types, and low resolution imaging techniques. Translating findings between model substrates and intact biomass is critical for evaluating enzyme performance. The most studied enzymatic system is the fungal free enzyme system, due to high enzyme production and saccharification performance. Anaerobic microbes produce large, multi-enzyme complexes known as cellulosomes, which have been shown to improve the yield of biomass conversion due to the high cellulose conversion rate and distinct enzymatic mechanisms. Here we employ fungal free enzymes, complexed cellulosomal systems<i>,</i> and both combined to investigate saccharification mechanisms on cellulose and pretreated biomass. Transmission and scanning electron microscopy of the biomass provides evidence for the different mechanisms of enzymatic deconstruction between free and complexed enzyme systems, and reveals a basis for the synergistic relationship between the two enzyme paradigms on process-relevant substrates. These results also demonstrate that the presence of lignin, rather than cellulose morphology, is more detrimental to cellulosome action than to free cellulases. As enzymatic conversion costs are a major economic driver for biorefineries, we are evaluating how different enzyme systems respond to organosolv, alkaline, and acidic biomass pretreatment methods.

Combination of enzyme paradigms and biomass pretreatment reveal novel saccharification mechanisms

249th National Meeting (2015)

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